Green vegetables which are to be canned according to the present invention are treated in a conventional blancher with hot water having a zinc or copper salt dissolved therein. The raw vegetables are blanched in hot water for the time and temperature suitable for that variety to effect the expulsion of occluded gases, activate or inactivate enzymes and effect the metal ion reaction. The temperature of the blanch is generally between about 150° and about 212°F and the duration of the blanch is for a suitable period of time, this time period varying somewhat with the character of the vegetable being canned. About three to about fifteen minutes at about 170° to about 190°F is a preferred time in the canning of green beans, peas and spinach.